At idle, the front and rear spark plugs fire simultaneously to increase the rate of combustion, resulting in improved fuel consumption.
At low speed, in light load mode, the ECM shifts the ignition timing to the front spark plug, where the combustion chamber temperature is relatively low, to improve fuel consumption.
At low speed in high load mode, the spark advance is transferred to the front spark plug and retarded on the rear side to improve torque while controlling engine knock.
At high speed, both the front and rear spark plugs fire at the same time to increase the rate of combustion, resulting in improved power.
Ignition timing control
The ECM computer stores in its memory the basic dependences of the ignition timing at various engine speeds and absolute pressures. The computer also corrects the ignition timing based on coolant temperature and intake air temperature.
Starting point and duration of fuel injection
The ECM computer stores in its memory the basic dependences of the duration of fuel injection at various engine speeds and air pressure in the intake manifold. The base value of the fuel injection duration, after it is read from the computer memory, is further adjusted in accordance with the signals sent from various sensors to obtain the final injection duration value.
By monitoring the parameters of the fuel injection process for a long time, the ECM computer detects malfunctions that occur in the fuel injection system for a long time and generates a diagnostic trouble code (DTC).
Knock sensor
The anti-knock system regulates the ignition timing in order to reduce knock to a minimum level.
Intake manifold absolute pressure sensor (IDA)
The MAP sensor converts intake manifold absolute air pressure into electrical signals to the ECM.
Air mass sensor (MAF) /intake air temperature sensor (IAT)
Air mass sensor (MAF) /intake air temperature sensor (IAT) contains a filament and a thermistor. It is located in the air intake duct. The resistance of the filament and thermistor varies with intake air temperature and airflow. The control circuit in the MAF sensor controls the current to maintain the set filament temperature. The control circuit converts the current into voltage, which is applied to the ECM.
Secondary heated oxygen sensor (secondary HO2S sensor)
Secondary oxygen sensor (HO2S) determines the oxygen content in the exhaust gases at the outlet of the three-way catalytic converter (TWC) and sends signals to the ECM, which changes the duration of fuel injection accordingly. To stabilize its output signal, the sensor has a built-in heater. The ECM compares the HO2S signal with the A/F sensor signal to determine the effectiveness of the catalytic converter. Secondary oxygen sensor (HO2S) located in a three-way catalytic converter.